Mercury vapor current converter



Dec. 9, 1947. M s

KMERCURY VAPOR CURRENT CONVERTER Filed July 10, 1946 Patented Dec. 9, 1947 2,432,433 MERCURY VAPOR CURRENT CONVERTER Herman Mees, Lodelinsart, Belgium, assignor to Ateliers de Constructions Electriques de Charleroi, Brussels, Belgium, a firm of Belgium Application July 10, 1946, Serial No. 682,535 In France July 19, 1945 In certain installations for converting alternating current into direct current, intended for instance for feeding electrolysis installations with a current capacity of the order of several tens of thousands of amperes, use may conceivably be made of mercury vapor current converters of high unitary power. The total power to be supplied can thus be assured by several polyanodic converters with a large number of anodes.

The design and construction of such converters present various difiiculties. If a normal central cathode analogous to that employed on converters of medium power is used, the relative position of the anodes and the cathode is such that the value of the drop in voltage in the arc increases in an appreciable manner and is no longer compatible with an economical converter yield.

In order to reduce the distance which separates the anodes from the cathode, an annular cathode of large diameter placed in such a way that its relative position with regard to the anode renders it possible to shorten the path of the arc may be provided, while retaining a suificient operating safety against the risk of backfiring.

Moreover, the operation of the heavy polyanodic converters may be complicated by a zone of high mercury vapor pressure developing around the cathode, an excess pressure which under certain conditions entails the elimination of the valve effect of the converter.

This high mercury vapor pressure is influenced by the intensity of the cooling of the walls of the converter on the one hand, and on the other hand by the distance which separates these Walls from the cathodic high pressure zone. In metal tank converters of great power the distance between these two elements may be such that the cooling of the walls has no effect on this high pressure mercury vapor cathodic zone; it is no longer possible, by acting on the cooling of the walls alone, to reduce the mercury vapor pressure in the immediate vicinity of the cathode.

It has already been proposed, in the case of annular cathodes, to arrange a tubular cooling member traversing the interior of the converter tank from the space comprised in the center of the annular cathode to the anode-carrying lid. This arrangement, while it may permit of an effective cooling of the mercury vapor high pressure cathodic zone, presents on the other hand great difiiculties of execution, especially that of a vacuum-proof joint at the cathode or at the anode-carrying lid, capable of making up for the expansion differences between the tubular network and the balance of the metallic tank of the converter.

The solutions heretofore suggested have not given a really practical solution to the problem 11 Claims. (Cl. 25027.5)

of a mercury vapor current converter for very high power magnitudes.

The present invention relates to a new arrangement of a mercury vapor converter with metal vat or tank for very high power magnitudes, characterized in that, in addition to providing an arrangement particularly adapted to reduce the value of the voltage drop in the arc and to prevent the formation of a cathodic region of high mercury vapor pressure capable of eliminating the valve effect of the converter, it also providesa facility and simplicity of construction which call for no special mounting or executing device.

To this end, there is arranged at the bottom of the metallic vat or tank of the converter an annular cathode of large diameter and with a small mercury volume and including but one packing joint with the tank, and on the inside of this tank a central cooling device made up wholly or in part of a tubular bundle, freely suspended from the anode-carrying lid of the converter and traversed by a cooling fluid, for example air.

The annular cathode is characterized by the fact that its effective section is limited on its outer side by a single or multiple ring of insulating and refractory material, such as quartz for instance, in a manner analogous to that used for conventional central cathodes.

It is moreover characterized by the fact that 7 its central portion is covered by a cup of insulating and refractory material such as quartz, placed over its concave surface and thus restricting, towards the center of the cathode, the effective section of the latter and the expansion region of the cathodic spot.

The assembly of the rings and of the cup delimiting the active region of the annular cathode is placed on a metal cathode bottom of large diameter and conventional construction, as for central cathodes. The expansion of the mercury towards the center of the cathode is limited by a core or a crown of metal added to the metal bottom of the cathode.

The cathode thus made up can be joined at the bottom of the metallic tank of the converter by a single packing joint which does not require special precautions such as are called for by the double joint of a normal annular cathode. As a matter of fact, no measure has to be taken to insure the simultaneous tightness of two flat concentric joints which may or may not be located on the same plane; moreover, no arrangement of elastic joint needs to be provided as in the case of the central cooling device traversing the tank assembly of the converter from the cathode bottom on the inside of the annular cathode to the anode-carrying lid.

A normal central cathode construction can therefore be applied to an annular cathode of large diameter of. this type, with the particularly attractive advantage of the reduction of the length of the arc, thus making it possible to obtain in a tank of large dimensions a drop in voltage in the are comprised between. admissible; values, practically independent of the general dimensions of the converter and. solely: a. function of the relative position or thecathode-with respect to the anode.

example, a View in section of a presently-preferred embodiment of a mercury vapor current converter of very high power according to the invention. Every detail not .indispensablei..toithe understanding of the inventionhas forthe sake of clarity, been omitted.

Fig. -2 is-aview of. a'modified detail. The metallic tank C of the converter is. pro"- vided' at its upper end with. an. anode-carrying lip P-the anodes being shown at. A:and at its lower end withla cathode K. (A. jacket G en.-

compasses the tank C, as shown, and. theLintermediate space, coextensive with the peripheral extent of the wall of thetank and. with its. conical bottom, may house cooling meansin the: form: of conduits of any suitable. cross section; Alternatively, and as shown, cooling .loafllesimmay. be provided extending over the entire peripheraLsurfaceof tank C and over its conical. bottom. A cooling fluid such as air. may be. blown through the aforesaid intermediate space, use being made for this purpose of any suitable circulating. device suchas a blower, fan, pump: or the like (not shown). The stream of cooling: fluid, flowing by in contact with'bafilesm, Withdrawsheat trans; mitted therethrough.

The cathode K is made up of a sheet metal plate p constituting the bottom of the cathode and can be cooled by suitable means, such as baffles or vanes 02. In its central portion, the cathode is provided with-a core 71/ for limiting the extent of the mercury.-

The extent orthe cathode: may be limited toward the outside, for instance by a quartz ring a. f. a shape similar to that oi the outer rings of conventional central cathodes-r Toward the center, this extentislimited by a quartz-cup a positioned with its open side down-,as shown;

and'covering the central metal core -12. The cup a thus prevents the cathodic action frcrribe'coming localized: at the central metal part oi the cathode and renders possible the free return to the cathode of the liquid mercury droplets which are condensed on its convex surface, l

The entire cathode assembly thus= constituted isfixed to the bottom of the tank C ofthe converter by a conventional" central cathode joint 1'; for example of the typewith an intermediate annulus.

The relative position of the cathode and the anodes may be identical to that of a central cathode converter with a low voltage drop-in-the arc, sothat the'drop-in voltage ofthe-arc of the annular cathodic converter remains of the same order of magnitude notwithstanding the greater number of anodes united in one and thesame tank. and. consequently, in spite of the; greater unitary power or the converter;

In the. illustrated embodiment, in. order to reduce the distancebetween the highimercuruvapor section (above the; cathode) and: the Lcooling means, in this case the means-m: onitlieperipliery of: thewall and" conical bottom: of tanlnc'of the On the attached sheet of drawingFig- 1. diae grammatically shows, by way of a non-restrictive;

directs the air to the fan blades.

converter, a bundle of tubes 'I is arranged, in freely suspended. manner, on the anode-carrying lint P; the tubes depending down into the mercury vapor high pressure cathodic region.

The tubes T terminate in a single tubular return conduit R which is likewise suspended from lid P and which houses the electrically-driven fan. V'suppo-rted from spider w. The fan V sets theccol ing air into motion. A cup-shaped baflle member c;-arranged as shown on the drawing, Each tube of the: bundle T is thus traversed by air set into motion in this manner, so that from the several inlets-e to the several outlets 8 there is a fiow in parallel of a plurality of streams of air. The inlets e of. the tubes and the u-tletg of the central return. conduit R; ion the air are disposed inadjacent'..portion s o-f the anode-carrying lid P.

this way th'e cooling action is brought; directly to the. inside of the mercury vapor high pressure'cathodic zone.

Thenumber of tubes comprising the tubebundies-.may, of course, be varied, the number being showneon: the. drawing being merely illustrative. The: downward extent or the several tubes, the configuration of which as shown is preferably L shaped" in charactenissuch that the high pressure. region is penetrated thereby. The L- configurati'on may bevaried however, and the tubes may for example-be-incurvedtoward the high pressure. mercury vapor pressure region, as shown for example in the detail of Fig. 2, s0 as to increase the influence of the cooling on the latter;

The cooling tubes Tmay;if desired; be arranged in. series-with. the. cooling device whereby a common source of power-fan, blower or the like-may: be. used. for. circulatingfluid through both cooling. arrangements. The circulation is established; sothat. the cooling fluid circulates from the. top of. thetan-ktoward'the cathode;

The: diameter of the tubes- T is not critical" and may be; varied. within considerable limits; The tubes arepretera-bly'made of metal.

The cooling device for the high pressurem'ercury vapor cathodiczone; rea'lizedbythe present invention, therefore presents, with relation to prior arrangements; the double advantage of a complete cooling efi'icacy for the high pressure zone, combined with a, simplicity of. construction perfectly adaptable to the metallic tanks of converters of current construction.

Havingtl'ius. disclosed. the invention, what is claimed" is;

'1..In a i high-power mercury vapor current converter, a metallictank, an anode onsaid tank, a mercury cathode contactin the metallic bottom" of said" tank, means for limiting the outward extent ofsaid' cathode, and means for limiting the inward" extent of said cathode, whereby thezone" of high mercury vapor. pressure which tends to be established" above said cathode; is. vcom-mensuratel'y. circumscribed;

2.. In a1'high-power mercuryvapor current converter; ametallic tank; an anode on said tank, a;::mer.curyr cathode on the metallic bottom of said': tank,.. means for limiting the outward extent of said cathode, means for limitingthe inwardrextent ofsaid cathode, whereby the zone of. higlumercury vapor: pressure which tends to be. established above said cathodeiscommensurately circumscribed, and cooling means-freely suspended. fromsa-id lid and extending downwardlyr'intoisaid. zones whereby the said tendency to establish a high pressure in said zone is minimized.

3. In a high-power mercury vapor current converter, a metallic tank, an anode on said tank, a mercury cathode on the metallic bottom of said tank, means for limiting the outward extent of said cathode, and means for limiting the inward extent of said cathode, whereby the zone of high mercury vapor pressure which tends to be established above said cathode is commensurately circumscribed, said first-named means comprising a refractory insulating ring encompassing the outer portion of said cathode.

4. In a high-power mercury vapor current converter, a metallic tank, an anode on said tank, a mercury cathode on the bottom of said tank, means for limiting the outward extent of said cathode, and means for limiting the inward extent of said cathode, whereby the zone of high mercury vapor pressure which tends to be established above said cathode is commensurately circumscribed, said second-named means comprising a centrally located metallic core and a cup of insulating and refractory material covering said core.

5. In a high-power mercury vapor current converter, a metallic tank, an anode on said tank, a mercury cathode on the metallic bottom of said tank, means for limiting the outward extent of said cathode, and means for limiting the inward extent of said cathode, whereby the zone of high mercury vapor pressure which tends to be established above said cathode is commensurately circumscribed, and means including a single annular sealed joint for connecting said bottom to said tank.

6. In a high-power mercury vapor current converter, a metallic tank, a mercury cathode at the bottom of the tank, means for restricting the outward and inward extent of said cathode, whereby a corresponding zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, said cathode and anodes being symmetrically arranged with respect to the central axis of said tank, a tubular bundle freely suspended from said lid and extending downwardly into the said zone, and means for circulatin cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized.

7. In a high-power mercury vapor current converter, a metallic tank, a mercury cathode on the bottom of the tank, means for restricting the outward and inward extent of said cathode, whereby a correspondingly restricted zone of high mercury vapor pressure tends to be established above said cathode, an anodecarrying lid on said tank, a tubular bundle freely suspended from said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, the inlets to and outlets from said tubular bundle being disposed in adjacent portions of said lid, and said cathode and anodes being symmetrically arranged with respect to the central axis of said tank,

8. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid and extending downwardly into the said zone,

means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially L -sl1aped conduits whereby a plurality of streams of cooling fluid traverse said conduits in parallel, and a tubular shaft common to said conduits and constituting an outlet passage for said streams.

9. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid and extending downwardly into the said zone, means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially L-shaped conduits whereby a plurality of streams of cooling fluid traverse said conduits in parallel, a tubular shaft common to said conduits and constituting an outlet passage for said streams, and means for instigating said streams disposed in said tubular shaft.

10. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid and extending downwardly into the said zone, means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially L-shaped conduits whereby a plurality of streams of cooling fluid traverse said conduits in parallel, and a tubular shaft common to said conduits and constituting an outlet passage for said streams, each said conduit having a portion curved into said zone.

11. In a high-power mercury vapor current converter, a, metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, cooling means freely suspended from said lid and extending downwardly into the said zone whereby the tendency to build up high pressure in said zone is minimized, a tubular outlet shaft mounted on said lid and in which said cooling means terminate, a cooling jacket about said tank, and means for producing a stream of cooling fluid through said cooling jacket, through said cooling means and out through said outlet shaft.

HERMAN MEES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,958,247 Prince May 8, 1934 2,157,913 Mehls May 9, 1939 I FOREIGN PATENTS Number Country Date 375,447 Great Britain June 30, 1930 483,620 Great Britain Apr, 22, 1938 500,530 Great Britain Feb. 10, 1939 

